James Stirton, who found it in his backyard, was initially mystified by the object's appearance. The 20kg heap of tangled carbon fibre and steel stuck out like a sore thumb from the dry scrubland of his cattle farm in Queensland, Australia.

"I was just riding along on my bike and it was beside the road, beside a track out in the paddock," Mr Stirton said.

"I just wondered what it was so I went over and had a look at it and I figured it must have fallen from the sky because there's no tracks or traffic or anything out here."

He added: "I know a lot about sheep and cattle but I don't know much about satellites. But I would say it is a fuel cell off some stage of a rocket."

Brisbane Planetarium curator Mark Rigby was asked to examine the object, which landed in the small town of Cheepie, west of Charleville in November last year.

He said there was "no doubt" it was a helium or nitrogen tank from a rocket, probably one that had been used to blast a U.S. solar satellite into space more than 18 months ago.

"I looked at what had been coming down around that time and orbits and things like that and managed to narrow the time frame based on when the farmer found it," he told the Sydney Morning Herald.

"This particular object was predicted for re-entry (into the Earth's atmosphere) at 11.47am Australian Eastern Standard time on November 1, 2007, which would have put it near Indonesia.

"I don't know why, but I think it has just sort of limped on a bit and ended up in Charleville."

After checking space flight records, Mr Rigby said the rocket had likely been launched from Cape Canaveral in Florida on October 26, 2006.

It was used to send up one of two Stereo satellites into orbit to study the sun.

Helium or nitrogen tanks are used to pressurise the rocket's fuel systems and also to manoeuvre the spacecraft.